Our laboratory has continued investigations of photodynamic therapy (PDT) for the treatment of thoracic malignancies by sensitization of malignant cells with dihematoporphyrin ether (DHE) followed by illumination with 630 nM light. Since October of 1987 we have investigated the use of light scattering media, intra-lipid, in different concentrations to improve the efficacy of PDT. We have found that low concentrations of intra-lipid will provide greater cytotoxicity via PDT, with greater light-scattering effects despite a loss of the sensitizer from the cells during the period of incubation with the intra-lipid. Using a phantom plexiglass model of the thoracic cavity, we have defined what the optimal light scattering concentration in this model is for intra-lipid in order to provide equal illumination to all surfaces. We have quantitated light scattering using a photodiode detection system, constructed by the Bioengineering Division. We are now investigating different in vitro PDT sensitivities of various thoracic, oncologic cell lines including a small-cell lung cancer variant, a large-cell carcinoma of the lung, mesothelioma, normal lung fibroblasts and an adenocarcinoma. For each of these cell lines we are defining fluourescence characteristics of the cells, cell size, cell protein, and inherent sensitivity to low energy phototherapy. The role of LDL receptors in the delivery of DHE at a cellular level is also being investigated. In preparation for conjugation of a monoclonal antibody to the sensitizor, in vitro and in vivo studies of PDT of a transformed fibroblast line, 45342 have been performed showing sensitivity of this line to PDT both in vitro and in vivo. We have now treated 9 patients with endobronchial disease with PDT and have made a movie demonstrating the technique of phototherapy. Two patients with recurrent ovarian carcinomatosis have been treated with intraabdominal PDT.